(1) Field of the Invention
The present invention relates to a photoresist stripping composition for removing photoresist in manufacturing of a device circuit of a liquid crystal display panel, and more particularly, to a photoresist stripping composition designed for a single wafer treatment method utilizing an air knife process as well as the dipping photoresist stripping process.
(2) Description of the Related Art
A semiconductor integrated circuit and a device circuit of a liquid crystal panel have very fine structures. The fine circuits are generally fabricated by uniformly coating a photoresist on an insulating film or a conductive metal film (such as an oxide film or an Al alloy film respectively), coated on a substrate, and exposing and developing the photoresist to form a certain pattern, and etching the metal film or insulating film by using the patterned photoresist as a mask, and thereafter, by removing the unnecessary photoresist.
A photoresist stripping composition is used in removing the photoresist from a substrate. In general, the stripping composition should have a high stripping force at both low and high temperatures, and should leave no residues on the substrate. Further, a desirable stripper should not corrode a metal film, while causing little hazard to both humans and the environment considering the large amount of stripping composition used in fabricating a large-scale liquid crystal display panel circuit.
To meet the above requirements, various photoresist stripping compositions have been suggested. For example, the U.S. Pat. No. 5,480,585 and the Japanese Patent Hei. 5-181753 disclose organic strippers comprising alkanolamine of the structural formula H3-nN((CH2)mOH)n (where m is 2 or 3, and n is 1, 2 or 3), sulfone compound or sulfoxide compound and a hydroxyl compound expressed by the structural formula C6H6n(OH)n (where n is 1, 2 or 3). The Japanese Laid-open Patent 4-124668 discloses a photoresist stripping composition including an organic amine of 20-90% by weight, phosphoric ester surfactant of 0.1-20% by weight, 2-butyne-1,4-diol of 0.1-20% by weight, and the remainder glycolmonoalkylether and/or aprotic polar solvent. For the glycomonoalkylether, ethyleneglycolmonoethylether, diethyleneglycolmonoethylether, or diethyleneglycolmonobutylether is used and for aprotic polar solvent, dimethylsulfoxide or N,N-dimethylaceteamide is used. The amount of the 2-butyne-1,4-diol and phosphoric ester surfactant was controlled, to the extent not sacrificing the stripping force, to prevent the corrosion of a metal film such as aluminum and iron.
The Japanese Patent Hei. 8-87118 discloses a stripping composition comprising 50 to 90% by weight of N-alkylalkanolamine and 50 to 10% by weight of dimethylsulfoxide or N-methyl-2-pyrrolidone. It states that even under hard stripping conditions the composition including N-alkylalkanolamine and the organic solvents prevent the formation of non-soluble impurities, and thus, leaves no residues on the substrate.
The Japanese Patent Laid-open Sho. 64-42653 discloses a photoresist stripping composition comprising over 50% by weight of dimethylsulfoxide (more desirably over 70% by weight), 1 to 50% by weight of a solvent selected among diethyleneglycolmonoalkylether, diethyleneglycoldialkylether, .gamma.-butyrolactone and 1,3-dimethyl-2imidazoledinon, and 0.1-5% by weight of nitrogen-including organic hydroxyl compound such as monoethanolamine. It states that the amount of dimethylsulfoxide less than 50% by weight causes great reduction in stripping force, while the amount of nitrogen-including organic hydroxyl compound solvent over 5% by weight corrodes the metal film such as aluminum.
Depending on the constituents of the compositions and the ratio thereof, the aforementioned stripping compositions exhibit greatly different characteristics in photoresist stripping force, metal corrosion properties, the complexities of a rinsing process following the stripping, environmental safety, workability and price. Such varying degrees of characteristics of the stripping compositions have led many researchers to search for the best compositions of maximum capabilities under various processing conditions.
However, the prior research has been largely directed toward developing stripping compositions suitable for the dipping method where the etched semiconductor integrated circuits or the device circuits of a liquid crystal display panel are immersed in a stripping composition to remove the photoresist. Typically, the conventional compositions designed for the dipping method show good chemical properties, such as a good stripping force, non-corrosiveness of metal and safety to humans. Unfortunately, however, these compositions have many shortcomings when used for a single-wafer treatment method using an air knife process, which is gaining an increasing popularity because of the relatively small amount of the stripping composition required. These shortcomings include less stripping force and a corrosion of metal. More importantly, residual impurities are left on the substrate, largely due to the different physical surface characteristics between the bare glass and the insulating or conductive metal film, such as an ITO film, an aluminum, chrome, silicon-nitride film and an amorphous silicon film on which the photoresist is formed.
Accordingly, the photoresist stripping compositions having the properties suitable not only for the dipping method but also for the single-wafer treatment method using an air knife process has a great demand in the industry.